Sciencemadness Discussion Board

31% and 37%

chemynooby2 - 28-5-2009 at 23:03

Lets say someone needed 100ml of 37% HCl, but he can only get 31% HCl how much extra HCl needs to be used?

stoichiometric_steve - 28-5-2009 at 23:09

31/37*X

len1 - 28-5-2009 at 23:41

37% HCl - strictly speaking % is a ratio, and so dimensionless - you cant get HCl at that strength at RT.

Theres an interesting point regarding the two numbers in the title -

37/32 ~ 1.16 the denisty of concentrated HCl at RT!

Why is this of interest - because some sell 32% HCl and others "a more concetrated version" at 37% - when its actually one and the same thing - H2O saturated in HCl at RT.

370gms HCl/L

or

320 gms HCl/kg

Panache - 29-5-2009 at 02:30

Quote: Originally posted by len1  
37% HCl - strictly speaking % is a ratio, and so dimensionless - you cant get HCl at that strength at RT.

Theres an interesting point regarding the two numbers in the title -

37/32 ~ 1.16 the denisty of concentrated HCl at RT!

Why is this of interest - because some sell 32% HCl and others "a more concetrated version" at 37% - when its actually one and the same thing - H2O saturated in HCl at RT.

370gms HCl/L

or

320 gms HCl/kg


always wondered about that, Sigma if i recall in Australia used to sell winchesters of 37%, me in my nonesensical wonder always thought it fumed more, HA!

chemynooby2 - 29-5-2009 at 09:54

119.3ml?

Thanks for the info! :) Yeah, there are so many scams out there in the chemical world. :mad:

Magpie - 29-5-2009 at 11:21
Quote:

37% HCl - strictly speaking % is a ratio, and so dimensionless - you cant get HCl at that strength at RT


Len, my lab manual says that concentrated HCl is 12M and is 37.3% HCl by weight.

len1 - 29-5-2009 at 14:58

Yes Magpie thanks for the correction. Checking the solubility of HCl I found 720gms in 1L H2O or, what amounts to the same thing, at 20C water absorbs 475 its own volume of HCl gas. That gas weighs 475*36.5/24.1 = 719gms in 1kg of water.

Thats 719/1719 = 42% HCl - something Ive never seen, but is apparently physically possible.

The reason you dont see it is that by definition this HCl of course boils at 20C, and even at 38% it boils at 49C. The stuff of commerce boils at ~ 85C and is 32% HCl, or 370gms/L HCl.